Heavy Quark Effective Theory For Mesons

Physics Reports-review Section of Physics Letters, 1997

The approximate symmetries of Quantum ChromoDynamics in the infinite heavy quark (Q = c, b) mass limit (mQ → ∞) and in the chiral limit for the light quarks (mq → 0, q = u, d, s) can be used together to build up an effective chiral lagrangian for heavy and light mesons describing strong interactions among effective meson fields as well as their couplings to electromagnetic and weak currents, including the relevant symmetry breaking terms. The effective theory includes heavy (Qq) mesons of both negative and positive parity, light pseudoscalars, as well as light vector mesons. We summarize the estimates for the parameters entering the effective lagrangian and discuss in particular some phenomenologically important couplings, such as gB * Bπ. The hyperfine splitting of heavy mesons is discussed in detail. The effective lagrangian allows for the possibility to describe consistently weak couplings of heavy (B, D) to light (π, ρ, K * , etc.) mesons. The method has however its own limitations, due to the requirement that the light meson momenta should be small, and we discuss how such limitations can be circumvented through reasonable ansatz on the form factors. Flavour conserving (e. g. B * → B γ) and flavour changing (e. g. B → K * γ) radiative decays provide another field of applications of effective lagrangians; they are discussed together with their phenomenological implications. Finally we analyze effective lagrangians describing heavy charmonium-like (QQ) mesons and their strong and electromagnetic interactions. The role of approximate heavy quark symmetries for this case and the phenomenological tests of these models are also discussed.

Physical Review D, 1998

In this paper we present a detailed formulation for a recently proposed effective field theory to describe the nonperturbative QCD dynamics of heavy mesons. This effective theory incorporates with heavy quark symmetry (HQS) and the heavy quark effective theory (HQET). Heavy mesons in this theory are constructed as composite particles of a heavy quark bounded with the light degrees of freedom. The heavy meson properties in the heavy quark limit and the 1/m Q corrections can then be explicitly evaluated from this effective theory. All the basic parameters of the HQET, namely, the heavy quark mass m Q , the heavy meson residual mass Λ, and the HQS breaking mass parameters λ 1 and λ 2 , are consistently determined. λ 1 is found to be small due to a large cancellation between the heavy quark kinetic energy and the chromo-electric interaction between the heavy quark and light degrees of freedom. We also evaluate the Isgur-Wise function, the decay constant, and the axial-vector coupling constant of heavy mesons.

Nuclear Physics B - Proceedings Supplements, 2009

The mass shifts of the P -wave Ds and Bs mesons due to coupling to DK and BK channels are calculated in the coupling channel model without fitting parameters. The strong mass shifts down for 0 + and 1 + ′ states have been obtained, while 1 + ′′ and 2 + states remain almost in situ. The masses of 0 + and 1 + ′ states of Bs mesons have been predicted.

International Journal of Modern Physics A, 1994

Extra symmetries are shown to exist in the effective theory of heavy quarks when both quarks and antiquarks with the same velocity are included. These symmetries mix the quark with the antiquark sector and they resemble the axial type of symmetries. Together with the known flavor and spin symmetries they form a u(4) algebra when a single flavor is considered. It is shown that the full U(4) set of symmetries breaks spontaneously down to U(2)⊗U(2). The Goldstone modes corresponding to the spontaneously broken currents are identified and their relation to physical particles is discussed. Finally, the precise connection of this theory with the fundamental QCD is derived and it is investigated under some approximations. Some physical processes where these extra symmetries may be relevant are pointed out.

Proceedings of 10th International Workshop on Charm Physics — PoS(CHARM2020), 2021

We review heavy quark flavor and spin symmetries, their exploitation in heavy meson effective theories and the flavored couplings of charmed and light mesons in the definition of their effective Lagrangians. We point out how nonperturbative continuum QCD approaches based on Dyson-Schwinger and Bethe-Salpeter equations can be used to calculate strong and leptonic decays of open-charm mesons and heavy quarkonia. The strong decay * → serves as a benchmark, as it is the only physical open-charm observable that can be related to the effective Lagrangian's couplings. Nonetheless, a quantitative comparison of * , , * and * * couplings for a range of off-shell momenta of the-meson invalidates SU(4) symmetry relations between these couplings. Thus, besides the breaking of flavor symmetry by mass terms in the Lagrangians, the flavor-symmetry breaching in couplings and their dependence on the-meson virtuality cannot be ignored. We also take the opportunity to present new results for the effective / and / * couplings. We conclude this contribution with a discussion on how the description of pseudoscalar and vector , , and meson properties can be drastically improved with a modest modification of the flavor-dependence in the Bethe-Salpeter equation.

Physics Letters B, 1993

We present a heavy quark description of quarkonium states and an effective lagrangian describing those interactions with chiral bosons and photons which occur in a soft-exchange-approximation regime. The formalism is expected to be valid for an intermediate heavy quark mass (up to = 80 GeV) and is based on the approximate validity of the heavy quark spin symmetry and velocity superselection rule. Some applications to radiative and hadronic transitions are discussed.

Physics Letters B, 2004

We study heavy–light meson resonances with quantum numbers JP=0+ and JP=1+ in terms of the non-linear chiral SU(3) Lagrangian. At leading order a parameter-free prediction is obtained for the scattering of Goldstone bosons off heavy–light pseudo-scalar and vector mesons. The recently announced narrow open-charm states observed by the BABAR and CLEO Collaborations are reproduced. We suggest the existence of states

2002

Recently we have proposed a new level-classification scheme of hadrons with a manifestly covariant framework. In this scheme the requirement of chiral symmetry on the light quark leads to a prediction of existence of new type of scalars XB, XD and axial-vectors XB * , XD * as the chiral partners of ground state pseudoscalar B, D and vector B * , D * mesons, respectively. They belong to "relativistic S-wave states," and are discriminated from the conventional P -wave mesons with jq = 1/2 appearing in the heavy quark effective theory. In this talk we examine the properties of these chiral mesons: The mass-splittings between the respective chiral partners are predicted to be equal, and the decay widths of one pion emission of XB, XD, XB * and XD * are to take the same value due to both chiral and heavy quark symmetries. Some experimental indications for existence of XB and XD * are also given, which are consistent with the above prediction. * ) Here the normalization of states |B(0) ≡ a † B(0) |0 , etc. are used, where [a B(p) , a † B(p ′ ) ] = δ (3) (p − p ′ ).

The European Physical Journal C

Inspired by the lower statistical information in the bottom sector, in this paper, we calculate the masses and the strong decays of excited B and $$B_s$$ B s mesons in the framework of heavy quark effective theory (HQET). Using an effective chiral Lagrangian approach based on heavy quark spin-flavor and light quark chiral symmetry, we explore the flavor independent parameters $$\varDelta _F^{(c)} = \varDelta _F^{(b)}$$ Δ F ( c ) = Δ F ( b ) and $$\lambda _F^{(c)} = \lambda _F^{(b)}$$ λ F ( c ) = λ F ( b ) to calculate the masses of experimentally unknown bottom mesons. Our predictions are consistent with the available experimental results and other theoretical studies. Their strong decay to the ground state bottom mesons plus light pseudoscalar mesons is calculated in terms of the square of the couplings $$g_H$$ g H , $$g_S$$ g S , $$g_T$$ g T , $$g_X$$ g X , $$g_Y$$ g Y , and $$g_R$$ g R . The weighted average value of the couplings $$g_H$$ g H , $$g_S$$ g S and $$g_T$$ g T is obta...

Physics Letters B, 1992

We modify a chiral effective lagrangian recently suggested to describe interactions of the light pseudoscalars with mesons containing a heavy quark, so as to incorporate light vector resonances, such as ρ, etc. The modification uses the hidden gauge symmetry approach. As a preliminary example we present an application to the semileptonic D → K ⋆ decay.